PURPOSE: To provide a compact discharged gets processing device capable of performing an efficient discharged gas processing.

CONSTITUTION: There is provided a filter device capable of removing solid substances from discharged gas. There is provided a heating device H for heating the discharged gas. There is provided a harmful gas removing device R for removing harmful gas from the discharged gas. The filter device F, the heating device H and the harmful gas removing device R are arranged in this order within one housing 4. There is formed a discharged gas flow passage 5 for guiding the discharged gas in the order to the filter device F, the heating device H and the harmful gas removing device R. A number of heat exchanging pipes 2 are arranged in side-by-side relation in a substantial equal spacing over an entire width of cross section crossed at a right angle or substantially at a right angle with a direction of the discharged gas flow passage 5 within the discharged gas flow passage 5.